This invention relates to transmission line coupling devices for high frequency transmission lines, such as used for microwaves. Particularly, the invention relates to rotatable transmission line couplings in which multiple rotatable transmission line members are mechanically coupled to the outside of the transmission line system for performing a variety of functions and the multiple transmission lines are capable of operating over distinct frequency bands while simultaneously rotating the orientation of the polarization of each transmission line coupling in each of its respective waveguide. A typical application is that of a waveguide coupling which rotates the plane of polarization of the waves transmitted through the device by external rotary energy source means.